[llvm-profgen] Use hot threshold for context merging and trimming

[wenlei]

Summary

Without preinliner, we need to tune down the cold count cutoff to merge/trim more context to limit profile size for large components. However it doesn't make sense for cold threshold to be higher than hot threshold, so we now change to use hot threshold as merging/trimming cut off instead.

[hoy]

llvm/tools/llvm-profgen/ProfileGenerator.cpp

431

Does it still make sense to keep this? Would profile summary builder use this value?

[wenlei]

llvm/tools/llvm-profgen/ProfileGenerator.cpp

431

Profile summary builder still use it, but the removed tuning was only needed for merging/trimming. Now that merging/trimming changed to use hot threshold, the tuning is no longer needed either. The tuning may not general enough for a good cold threshold.

[hoy]

llvm/tools/llvm-profgen/ProfileGenerator.cpp

431

Sounds good.

llvm/test/tools/llvm-profgen/merge-cold-profile.test

 ; Used the data from recursion-compression.test, refer it for the unmerged output
-; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t1 --compress-recursion=-1 --profile-summary-cold-count=8
+; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t1 --compress-recursion=-1 --profile-summary-hot-count=8
 ; RUN: FileCheck %s --input-file %t1
 
 ; Test --csprof-trim-cold-context=0
-; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t2 --compress-recursion=-1 --profile-summary-cold-count=100 --csprof-trim-cold-context=0
+; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t2 --compress-recursion=-1 --profile-summary-hot-count=100 --csprof-trim-cold-context=0
 ; RUN: FileCheck %s --input-file %t2 --check-prefix=CHECK-KEEP-COLD
 
 ; Test --csprof-merge-cold-context=0
-; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t3 --compress-recursion=-1 --profile-summary-cold-count=10 --csprof-merge-cold-context=0
+; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t3 --compress-recursion=-1 --profile-summary-hot-count=10 --csprof-merge-cold-context=0
 ; RUN: FileCheck %s --input-file %t3 --check-prefix=CHECK-UNMERGED
 
 ; Test --csprof-frame-depth-for-cold-context
-; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t2 --compress-recursion=-1 --profile-summary-cold-count=100 --csprof-trim-cold-context=0 --csprof-max-cold-context-depth=2
+; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t2 --compress-recursion=-1 --profile-summary-hot-count=100 --csprof-trim-cold-context=0 --csprof-max-cold-context-depth=2
 ; RUN: FileCheck %s --input-file %t2 --check-prefix=CHECK-COLD-CONTEXT-LENGTH
 
 ; CHECK:     [fa]:14:4
 ; CHECK-NEXT: 1: 4
 ; CHECK-NEXT: 3: 4
 ; CHECK-NEXT: 4: 2
 ; CHECK-NEXT: 5: 1
 ; CHECK-NEXT: 6: 0

llvm/tools/llvm-profgen/ProfileGenerator.cpp

void CSProfileGenerator::postProcessProfiles() {
   }
 
   // Trim and merge cold context profile using cold threshold above. By default,
   // we skip such merging and trimming when preinliner is on.
   if (!EnableCSPreInliner || CSProfTrimColdContext.getNumOccurrences() ||
       CSProfMergeColdContext.getNumOccurrences()) {
     SampleContextTrimmer(ProfileMap)
         .trimAndMergeColdContextProfiles(
-            ColdCountThreshold, CSProfTrimColdContext, CSProfMergeColdContext,
+            HotCountThreshold, CSProfTrimColdContext, CSProfMergeColdContext,
             CSProfMaxColdContextDepth);
   }
 }
 
 void CSProfileGenerator::computeSummaryAndThreshold() {
-  // Update the default value of cold cutoff for llvm-profgen.
-  // Do it here because we don't want to change the global default,
-  // which would lead CS profile size too large.
-  if (!ProfileSummaryCutoffCold.getNumOccurrences())
-    ProfileSummaryCutoffCold = 999000;
-
   SampleProfileSummaryBuilder Builder(ProfileSummaryBuilder::DefaultCutoffs);
   auto Summary = Builder.computeSummaryForProfiles(ProfileMap);
   HotCountThreshold = ProfileSummaryBuilder::getHotCountThreshold(
       (Summary->getDetailedSummary()));
   ColdCountThreshold = ProfileSummaryBuilder::getColdCountThreshold(
       (Summary->getDetailedSummary()));
 }